1. Technical Field
The present invention relates to a linear vibrator.
2. Description of the Related Art
Generally, portable electronic devices, such as mobile phones, game players, mobile information terminals, etc., have various vibration generating units to prevent noise therefrom from disturbing other people. Particularly, such a vibration generating unit is installed in a cellular phone and used as a mute signal reception indicating unit. Recently, in accordance with the trend to provide a small and slim cellular phone, a reduction in the size and an increase in the function of a vibration generating unit installed in the cellular phone are also required.
At present, a vibration generating unit which is one of several signal reception indicating units used in a communication device, such as a cellular phone, converts electric energy into mechanical vibration by the use of a principle of generating electromagnetic force. That is, the vibration generating unit is used as a mute signal reception indicating unit in the cellular phone.
Meanwhile, a method in which mechanical vibration is generated by rotating a rotor having an eccentric weight has been used as a representative example of methods of operating vibration generating units according to conventional techniques. The rotation of the rotor is implemented by a commutator or brush motor structure which commutates currents through a contact point between the brush and the commutator and then supplies the currents to a coil of the rotor.
However, in the vibration generating unit having this structure, when the brush passes through a gap between segments of the commutator, mechanical friction, electric sparks or abrasion is induced, thus creating impurities, such as black powder, thereby reducing the lifetime of the vibration generating unit. To overcome these problems, a linear vibrator which can produce reliable linear vibration was proposed.
FIG. 1 is a sectional view of a linear vibrator according to a conventional technique.
As shown in FIG. 1, the linear vibrator 10 according to the conventional technique includes a casing 20, a bracket 30, a vibration unit 40 and a spring member 50. The casing 20 defines a space therein. The bracket 30 supports thereon a coil 32 which forms a magnetic field using an electric current applied to the coil 32. A damper member 34 is provided on the bracket 30. The vibration unit 40 includes a yoke 42 which has a hollow space therein and is closed on one end thereof, a magnet 44 which is installed in the hollow space of the yoke 42 and provided with a plate yoke 43 attached to the lower surface thereof, and a weight 46 which is fitted over the circumferential surface of the yoke 42. The spring member 50 is coupled to the upper surface of the casing 20 to elastically support the vibration unit 40 such that it linearly vibrates. The yoke 42 includes a disk part 42a and a rim part 42b which is bent downwards from the outer edge of the disk part 42a and extends a predetermined length.
In the linear vibrator 10 having the above-mentioned construction, when power is applied to the coil 32, the vibration unit 40 vibrates upwards and downwards by the spring member 50 due to interaction between a magnetic field which is generated by a magnetic circuit including the cylindrical magnet 44, the plate yoke 43 and the yoke 42, and an electric field generated by the coil 32.
However, in the case where external force is applied to the linear vibrator 10 when it is not in operation, because the vibration unit 40 is connected to the spring member 50, undesirable fine vibrations are caused which in turn cause the reliability of the linear vibrator 10 to deteriorate.
Furthermore, if an external force moves the vibration unit 40 in a horizontal direction or rotates it while it is in operation, the vibration unit 40 may come into direct contact with the casing 20, thus generating contact noise and causing parts in the interior of the linear vibrator 10 to impact each other.